1. Technical Field
The present invention relates backlights, and more particularly, to a lens for a backlight capable of uniform illuminance distribution, a backlight capable of preventing a light leakage phenomenon, and a backlight assembly having the same.
2. Discussion of the Related Art
A liquid crystal display device displays an image by using a separate light source. In other words, the liquid crystal display device does not emit light by itself. Therefore, the liquid crystal display device includes a lighting unit such as a backlight.
A cold cathode fluorescent lamp (CCFL) has been used as a conventional light source for the backlight. In some applications, the CCFL has been replaced with a light emitting diode (LED) element having features such as elongated life, low power consumption, light weight, and slim size.
A backlight may include a plurality of LED elements disposed as a surface light source on a plane for supplying light to a flat panel liquid crystal display device. In this configuration, the light emitted to an overhead area of the LED element (e.g., directly upward) has a greatest intensity; however, the intensity of the light gradually decreases from the overhead area to a peripheral area of the LED element. In other words, an illuminance distribution on a horizontal plane spaced a predetermined distance apart from the LED element exhibits a substantial Gaussian distribution, thus the light emitted from the LED element is not uniformly distributed over a wide area.
When such an LED element is used as a surface light source of the backlight, the LED elements should be arranged at small intervals. However, this increases the number of LED elements disposed on a plane and, in turn, the manufacturing cost of the backlight. Further, the light emitted from the LED element spreads to the overhead and peripheral areas of the LED element. Thus, for example, when some of the LED elements in the backlight are driven to locally supply light to an area of a liquid crystal display device, the light spreads to the overhead and peripheral areas of the LED element, thereby causing a light leakage phenomenon.
Accordingly, there exists a need for a backlight that includes a plurality of LED elements that provides uniform luminance distribution and that prevents a light leakage phenomenon.